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author:("Nguyen, nha")
1.  Myocardial blood flow measurement with a conventional dual-head SPECT/CT with spatiotemporal iterative reconstructions - a clinical feasibility study 
Cardiac single photon emission computed tomography (SPECT) cameras typically rotate too slowly around a patient to capture changes in the blood pool activity distribution and provide accurate kinetic parameters. A spatiotemporal iterative reconstruction method to overcome these limitations was investigated. Dynamic rest/stress 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) SPECT/CT was performed along with reference standard rest/stress dynamic positron emission tomography (PET/CT) 13N-NH3 in five patients. The SPECT data were reconstructed using conventional and spatiotemporal iterative reconstruction methods. The spatiotemporal reconstruction yielded improved image quality, defined here as a statistically significant (p<0.01) 50% contrast enhancement. We did not observe a statistically significant difference between the correlations of the conventional and spatiotemporal SPECT myocardial uptake K 1 values with PET K 1 values (r=0.25, 0.88, respectively) (p<0.17). These results indicate the clinical feasibility of quantitative, dynamic SPECT/CT using 99mTc-MIBI and warrant further investigation. Spatiotemporal reconstruction clearly provides an advantage over a conventional reconstruction in computing K 1.
PMCID: PMC3867729  PMID: 24380045
Dynamic SPECT; myocardial perfusion imaging; 99mTc-MIBI; SPECT/CT; spatiotemporal reconstruction; uptake rate constant
2.  Combined SPECT and Multidetector CT for Prostate Cancer Evaluations 
111In-capromab pendetide is an imaging probe for noninvasive detection of prostate cancer dissemination, and can be difficult to interpret because of low photon statistics resulting in noisy images with limited anatomical precision. We examined if a 16-slice multidetector computed tomography (MDCT) combined with single photon emission computed tomography (SPECT) could increase the impact on the clinical management and improve confidence in SPECT image interpretations in comparison to a relatively low-mA (limited resolution) CT. 17 scans were reviewed from a SPECT combined with low-mA CT scanner; 21 scans were reviewed from a SPECT combined with 16-slice MDCT scanner. Reports of the clinical interpretations from the imaging studies, additional examinations performed by referring physicians as a follow-up to the imaging results, and long-term clinical and laboratory follow-ups were used to define confidence of the SPECT/CT readings and impact of the readings on the patient management. The impact was defined as: the occurrence of the 111In-capromab pendetide interpretation resulted in additional imaging studies or biopsies. MDCT improved the quality and confidence in the characterization of small lymph nodes with or without uptake of 111In-capromab pendetide. The increased confidence with MDCT in SPECT/CT readings was evident in all cases reviewed in this study, and the impact on the clinical management was higher (8 out of 21) using SPECT/MDCT than the impact using SPECT combined with low-mA CT (2 out of 17). The dual-modality SPECT/CT provides a quantifiable benefit when MDCT is used instead of low-mA CT, particularly for prostate cancer evaluations using 111In-capromab pendetide.
PMCID: PMC3260786  PMID: 22267999
prostate cancer; capromab pendetide; SPECT/CT; MDCT; prostate specific membrane antigen (PSMA)
3.  Actions of a picomolar short-acting S1P1 agonist in S1P1-eGFP knock-in mice 
Nature chemical biology  2011;7(5):254-256.
Sphingosine 1-Phosphate Receptor 1 (S1P1) plays a critical role in lymphocyte recirculation and is a clinical target for treatment of multiple sclerosis. By generating a short-duration S1P1 agonist and mice where fluorescently tagged S1P1 replaces wild-type receptor, we elucidate physiological and agonist-perturbed changes in expression of S1P1 at a subcellular level in vivo. We demonstrate differential downregulation of S1P1 on lymphocytes and endothelia following agonist treatment.
doi:10.1038/nchembio.547
PMCID: PMC3430385  PMID: 21445057
4.  Combined SPECT and multidetector CT for prostate cancer evaluations 
111In-capromab pendetide is an imaging probe for noninvasive detection of prostate cancer dissemination, and can be difficult to interpret because of low photon statistics resulting in noisy images with limited anatomical precision. We examined if a 16-slice multidetector computed tomography (MDCT) combined with single photon emission computed tomography (SPECT) could increase the impact on the clinical management and improve confidence in SPECT image interpretations in comparison to a relatively low-mA (limited resolution) CT. 17 scans were reviewed from a SPECT combined with low-mA CT scanner; 21 scans were reviewed from a SPECT combined with 16-slice MDCT scanner. Reports of the clinical interpretations from the imaging studies, additional examinations performed by referring physicians as a follow-up to the imaging results, and long-term clinical and laboratory follow-ups were used to define confidence of the SPECT/CT readings and impact of the readings on the patient management. The impact was defined as: the occurrence of the 111In-capromab pendetide interpretation resulted in additional imaging studies or biopsies. MDCT improved the quality and confidence in the characterization of small lymph nodes with or without uptake of 111In-capromab pendetide. The increased confidence with MDCT in SPECT/CT readings was evident in all cases reviewed in this study, and the impact on the clinical management was higher (8 out of 21) using SPECT/MDCT than the impact using SPECT combined with low-mA CT (2 out of 17). The dual-modality SPECT/CT provides a quantifiable benefit when MDCT is used instead of low-mA CT, particularly for prostate cancer evaluations using 111In-capromab pendetide.
PMCID: PMC3260786  PMID: 22267999
Prostate cancer; capromab pendetide; SPECT/CT; MDCT; prostate specific membrane antigen (PSMA)
5.  Distinct Activities of the α-Catenin Family, α-Catulin and α-Catenin, on β-Catenin-Mediated Signaling 
Molecular and Cellular Biology  2004;24(6):2410-2422.
α-Catenin, an integral part of cadherin-catenin adhesion complexes, is a major binding partner of β-catenin, a key component of the Wnt pathway, which activates T-cell factor (TCF)/lymphoid enhancer factor (LEF) transcription and is often upregulated in cancers. Recently, we identified an α-catenin-related protein, α-catulin, whose function is poorly understood, as part of a Rho GTPase signaling complex. Here, based on evidence suggesting that α-catulin may associate with a β-catenin fraction, we investigated the role of α-catenin family members in β-catenin-mediated signals. Expression of the full length or a 103-residue region of α-catenin strongly inhibits the induction of the TCF/LEF-responsive TOPFLASH reporter in HEK293T cells expressing activated β-catenin or in cancer cells with constitutively upregulated Wnt signaling, whereas α-catulin expression had no effect. Interestingly, α-catulin expression attenuates the activation of the cyclin D1 promoter, a target of Wnt pathway signals. α-Catulin appears to inhibit Ras-mediated signals to the cyclin D1 promoter, rather than β-catenin signals, and the synergy between Ras and β-catenin required to fully activate this promoter. Data suggesting the involvement of Rho in this response are presented and discussed. These results suggest a novel function for α-catulin and imply that α-catenin and α-catulin have distinct activities that downregulate, respectively, β-catenin and Ras signals converging on the cyclin D1 promoter.
doi:10.1128/MCB.24.6.2410-2422.2004
PMCID: PMC355851  PMID: 14993280
6.  Replacement of Pre-T Cell Receptor Signaling Functions by the CD4 Coreceptor 
An important checkpoint in early thymocyte development ensures that only thymocytes with an in-frame T cell receptor for antigen β (TCR-β) gene rearrangement will continue to mature. Proper assembly of the TCR-β chain into the pre-TCR complex delivers signals through the src-family protein tyrosine kinase p56lck that stimulate thymocyte proliferation and differentiation to the CD4+CD8+ stage. However, the biochemical mechanisms governing p56lck activation remain poorly understood. In more mature thymocytes, p56lck is associated with the cytoplasmic domain of the TCR coreceptors CD4 and CD8, and cross-linking of CD4 leads to p56lck activation. To study the effect of synchronously inducing p56lck activation in immature CD4−CD8− thymocytes, we generated mice expressing a CD4 transgene in Rag2−/− thymocytes. Remarkably, without further experimental manipulation, the CD4 transgene drives maturation of Rag2−/− thymocytes in vivo. We show that this process is dependent upon the ability of the CD4 transgene to bind Lck and on the expression of MHC class II molecules. Together these results indicate that binding of MHC class II molecules to CD4 can deliver a biologically relevant, Lck-dependent activation signal to thymocytes in the absence of the TCR-α or -β chain.
PMCID: PMC2196103  PMID: 8996248

Results 1-6 (6)